This invention relates to couplings used for transmitting rotation from one shaft to another, and more particularly, to a coupling using an elastomeric belt with a retaining sleeve used to keep the belt in place.
Various types of flexible couplings have been used for connecting one shaft to another. These couplings compensate for relatively minor degrees of shaft misalignment which are normally encountered in manufacturing operations.
One type of prior art coupling uses two hubs, each hub having a plurality of projecting teeth extending from the hub face toward the other hub face. Such couplings, called jaw-type couplings, are sold by Lovejoy, Inc. of Downers Grove, Ill. The hubs are each mounted on one of the shafts. The teeth extending from each hub face are of a length so that they will be slightly separated from the other hub face when the coupling is assembled. The teeth, which are parallel to but overlap each other, are separated by spaces. An elastomeric element, often called a spider, occupies the plurality of spaces formed between adjacent teeth. Thus, the force from the teeth of the one hub is transmitted through the elastomeric element to the teeth of the other hub. These couplings operate with the elastomeric element in compression and have the characteristics of compactness, capable of transmitting large forces and continuing to transmit rotational forces even when the elastomeric element fails. This last characteristic can be an advantage or a shortcoming in that if the elastomeric element fails, the teeth of one hub strike the teeth of the other hub and continue to drive the driven shaft and any equipment to which it is connected. Thus, in an overload condition, the driven equipment is not protected by the coupling.
Another type of flexible coupling is illustrated in U.S. Pat. No. 5,139,460 by Hoyt, III et al. This coupling is similar to the above described coupling in that a pair of hubs each having extending teeth are mounted on their respective shafts. However, the teeth on one hub are parallel to and aligned with the teeth on the other hub. A belt surrounds the hubs and fills in the spaces between adjacent pairs of teeth. Projections on the belt engage receptacles on the hub teeth to prevent the hubs from moving apart. In this design, the belt operates in shear.
Advantages of this type of design are that the belt provides for misalignment between the shafts; the belt transmits power uniformly; the belt provides damping; and if the belt fails, the driven equipment is protected as it will essentially be disconnected from the drive shaft. Furthermore, this type of design allows the belt to be replaced without disassembling the hubs or moving the equipment connected to the shafts.
Another type of shear coupling is illustrated in U.S. Pat. No. 5,295,911 to Hoyt, III et al. This design illustrates teeth overlapping each other while using an elastomeric belt between overlapping teeth to transmit the torque. There is also shown a retainer ring surrounding the belt to keep the belt in place.
A problem arises with this coupling in that the elastomeric belts are subject to large and continuous forces during operation. Upon starting and stopping, the shear and compression forces on the elastomeric belt are further increased. The area on the belt between adjacent load transmitting projections is thinner and thus more prone to failure. Thus, there is a need to provide an elastomeric belt which has a longer life than previously used belts in shear couplings.
Another problem with prior couplings operated in shear which use an elastomeric belt is that the configuration and geometry of the hub teeth make it difficult to install and remove the elastomeric belt. Previously, the hub teeth on such shear couplings had the sides of the teeth parallel to each other. The hub teeth were rectangular in cross section. This made it difficult to insert and remove the projections on the elastomeric belt. There was a need for a belt and hub tooth design which made it easier to install and remove the belt from the hub.
Accordingly, it is an object of the invention to provide a flexible coupling which operates in shear and utilizes an elastomeric belt which has a longer life than prior belts. Related to this object is the object of providing an elastomeric belt which has a flexible pleated portion to absorb start-up forces, thereby extending the life of the belt.
It is a related object to provide a shear type flexible coupling which has an elastomeric belt having projections thereon which are received between the hub teeth in such a manner as to allow easy installation and removal from the teeth.
The invention disclosed herein provides a shear-type flexible coupling in which the teeth on the hubs are in parallel alignment and spaced from each other. A flexible elastomeric belt fills the gaps between adjacent pairs of teeth. A retainer band is mounted around the belt to keep the belt securely in place. The elastomeric belt has pleated portions which flex and absorb the start-up forces when the drive shaft begins rotating. The projections on the belt are wedge shaped to engage wedge shaped teeth on the hubs. This allows the belt to be more easily installed and removed than on prior shear type couplings.